The present invention relates in general to structural foundation repair and in particular to a method and apparatus for drilling a supporting pier to lift and support a structure from a foundation side.
Many types of structures, such as residential homes, commercial buildings and industrial equipment, are erected on foundations that are in turn supported by unstable soil rather than a load bearing formation such as rock. These foundations are typically concrete slabs and may include a footing that is wider than the foundation to spread the load of the foundation and carried structure. Ultimately the structural integrity and the level of the foundation and the carried structure are dependent on the stability of the underlying soil. Over time the stability of the underlying soil may change. These changes may include shifting of the soil and or subsidence of the underlying soil or portions of the supporting soil. Shifting of the soil may be caused by various geological and environmental conditions and/or the load carried by the structure. The changes in the supporting soil often result in damage to the structural integrity of the foundation and the carried structure and/or producing a non-level foundation. Left uncorrected the settling of the soil and lack of stability of the foundation may result in loss of part or all of the value of the foundation and carried structure. Due to the frequency of damage to foundations from soil settlement many systems have been attempted to stabilize the foundation and to correct positioning of the foundation.
The majority of methods and systems utilized to correct foundation damage is costly and often only provides a temporary solution or an incomplete solution. Many of the prior art foundation repair systems consist of driving piers into the underlying soil until refusal of insertion is attained. It is desired that the piers be driven until bedrock is reached or until the frictional resistance to driving of the pier corresponds to the compression weight of the supported structure. Once the piers are positioned in the ground hydraulic jacks are utilized to lift the foundation relative to the ground level. When the desired raised level is achieved the pier is connected to the foundation to secure the foundation in place, at least for the short term. Another constant aspect of the prior art foundation lifting systems is the utilization of brackets, or supports, that connect to the underneath side of the foundation. This positioning of the brackets on the underside of the foundation requires that a portion of the underlying soil be excavated from beneath the foundation.
In various situations it is necessary to raise and support the foundation within the perimeter of the foundation. Prior art methods and systems require cutting away a portion of the foundation and then excavating the soil from beneath the intact foundation to connect the lifting and supporting apparatus to the underside of the foundation. This additional excavation of the soil from beneath the intact foundation increases the time and cost of the project and increase the risk to workers as they position connections beneath the foundation.
Driving of piers, pilings or piles into the soil is a source of some of the most severe drawbacks of the prior art systems. Piers are typically driven into the ground utilizing a hydraulic mechanism until refusal and/or until the frictional resistance of the pier corresponds to the compression load of the foundation and structure. Very often bedrock is not encountered and the driven pier is supported by an unstable formation. It is also the case that the driven piers may pass through formations such as shale or other tight soils increasing the frictional force of driving the pier thereby providing misleading information as to contact with a suitable supporting formation. These geological formations may only provide temporary lifting and support of the foundation. Over time, changes in soil moisture content and other geological conditions may result in reduced or increased skin friction at the soil pier interface in these formations resulting in loss of stability from this formations.
Another problem with pier driving systems is maintaining a vertical alignment of the driven pier when the soil contains small boulders or other hard obstructions. As the pile is driven it may encounter several different soil formations and other material that will cause the pier to deviate from vertical. Piers may be twisted and even turned so that a portion extends horizontal relative to the intended pier path. These occurrences make it appear as though the pier has encountered a load bearing strata such as bedrock. The result being an expensive temporary solution or even another source of foundation problems.
Further, pier driven systems are limited on the diameter of pipe that may be used as a pier, thus decreasing the load strength of each pier. In addition, pier driven systems do not facilitate testing of the depth to the bedrock before driving the pier.
It is thus a desire to provide a method and apparatus for lifting and stabilizing a foundation that addresses some of these and other shortcomings of the prior art. It is a desire to provide a method and apparatus for lifting and stabilizing a foundation wherein a pier is placed in a substantially vertical position from a foundation to an underlying rock formation. It is a further desire to provide method and apparatus for lifting and stabilizing a foundation wherein a foundation may be lifted and stabilized from a periphery of the foundation. It is a still further desire to provide method and apparatus for lifting and stabilizing a foundation wherein lifting and supporting of a foundation may be from the edge of the foundation. It is a still further desire to provide a method and apparatus for lifting and stabilizing a foundation that does not require maintenance. It is a still further desire to provide a method and apparatus for lifting and stabilizing a foundation that does not require special soils be placed around the foundation to maintain its future performance. It is a still further desire to provide a method and apparatus for lifting and stabilizing a foundation that does not require drainage corrections around the foundation for performance.
In view of the foregoing and other considerations, the present invention relates to foundation repair wherein a foundation may be raised and stabilized from a stable geological formation, such as bedrock or other hard rock, without driving a pier.
It is a benefit of the present invention to provide a method and apparatus for lifting and stabilizing a foundation by drilling a hole from the foundation to a stable geological formation for placement of a pier.
It is a further benefit of the present invention to provide a method and apparatus for lifting and stabilizing a foundation from the periphery of the foundation.
It is a still further benefit of the present invention to provide a method and apparatus for lifting and stabilizing a foundation that does not require maintenance for continual support of a structure.
Accordingly, a method and apparatus for lifting and stabilizing a foundation is provided. The foundation and lifting system includes a pier having a top end and a bottom end, the pier being disposed in shaft drilled proximate the foundation to a desired underground formation suitable for supporting the foundation; a slab bracket connected to a side of the foundation and not supporting the foundation from the underside thereof, a jacking bracket attached to the top end of the pier and positioned below the slab bracket; and means for supporting the foundation positional between the jacking bracket and the slab bracket. This to rock support system prevents settling without regard to the supporting soil.
For brevity and clarity the present invention is described in relation to common residential and commercial structures supported on concrete slabs, and bedrock. However, it should be realized that the present invention may be applied to any structure or foundation, and any hard geological formation sufficient to support the structure may be utilized. For example, the present system and method may be utilized for construction and support of a deck or other structure proximate a hillside house adjacent a creek. A carbide bit may be used to drill a shaft into a rock formation at the bottom of the creek and the jacking bracket may be bolted to the wood beam to support the structure. Another example is utilization of the present invention is in the support of a retaining wall on a hillside experiencing slope failure. Utilizing the present invention the retaining wall is prevented from settling or sliding down the hill.
It is desirable to drill the shaft to an underground rock formation, such as bedrock, sufficient for stable and long term support of the foundation. Using a dirt drill bit a shaft is drilled to and into a geological formation until the formation does not allow a shaft to be created. Utilizing the dirt bit until drilling operations are prevented from making hole by the formation assures the acquisition of a formation suitable for support of the structure.
The pier, having a top end and a bottom end, is placed in the drilled shaft. It may be desired to clean any silt, cuttings or soughed material from the bottom of the hole before placement of the pier. It may be desired to drive the pier through any material at the bottom of the shaft. A cup may be connected to the bottom end of the pier to prevent the pier from cutting into the formation.
A slab bracket is provided for attachment to a side of the foundation to be supported. The side of the foundation may be exposed at the soil surface, by excavating soil from the perimeter of the foundation or cutting through the foundation. The present invention does not require support of the foundation from the underside of the foundation. The slab bracket is positioned above the drilled shaft and the positioned pier.
The slab bracket includes a face plate adapted for placement against the face of the foundation to be raised and a support plate extending outwardly from the face plate and foundation. The slab bracket may be connected to the foundation with bolts extending through the faceplate into the foundation. It may further be desired to utilize a cementing agent, such as an epoxy, to secure the bolts within the foundation. It may further be desired to have stabilizing legs positioned between the faceplate and the support plate of the slab bracket.
A jacking bracket is functionally connected to the top end of the pier and positioned below the support bracket of a slab bracket. The jacking bracket includes a shelf that may be connected by welding to a main post having a diameter for snugly disposing a portion of the top end of the pier therein. The jacking bracket may be connected to the pier in various manners including disposing a portion of the pier into the jacking bracket, welding the jacking bracket to the pier or threading the jacking bracket on the pier or a combination of methods. It is desirable to have a jacking bracket readily connectable to the pier after positioning the pier at a desired height. The current system desirably allows placement and securement of the pier in the shaft, and then a top portion of the pier may be removed at a level to attach the jacking bracket to achieve a sufficient spacing between the jacking and slab bracket for positioning of lifting and/or securement mechanisms.
It is desired to provide a space between the jacking and slab bracket for providing mechanisms for lifting and securing the foundation. The space provided allows the placement of a lifting mechanism such as, but not limited to, a hydraulic jack for raising the foundation to a desired location. Once the foundation is positioned in a desired location a supporting mechanism may be placed and/or connected between the jacking bracket and the slab bracket to maintain the foundation in a position relative to the supporting formation. The supporting mechanism may include concrete blocks and/or metal shims.
The present invention accomplishes placement of a pier between a foundation to be supported and a desired supporting ground formation by confirming existence of the supporting formation and the depth to the supporting formation. The present invention provides support a structure irrelevant of the characteristics of the soil or medium immediately underlying the structure.
The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.